The present invention relates generally to scraper blade mechanisms which are used to remove residual material from a conveyor belt. Belted conveyors are widely used to transport many types of bulk materials such as coal, gravel, crushed rock and the like. This type of conveyor generally consists of a belt having two ends spliced together to form a loop having an inside and an outside belt surface. The outside belt surface is generally more durable than the inside surface as the outside belt surface is designed to carry the bulk material. The belt is placed around two pulleys, a head pulley and a tail pulley, so that the belt comprises an upper carrying run and a lower return run. One of the pulleys is mechanically driven to rotate the belt about the head and tail pulleys. The belt is sometimes supported between the head and tail pulleys by idler rollers. Bulk material is loaded at the tail end of the conveyor belt and is conveyed by the rotation of the belt to the head end of the conveyor where the material is discharged.
As the bulk material is loaded and transported on the conveyor belt, some of the material may flow over the edge of the belt and fall onto the inner surface of the return run of the conveyor belt. Such material is known as fugitive material. Such fugitive material will ride the return run of the belt and will be carried into the tail pulley where it will become crushed between the inner surface of the belt and the tail pulley, potentially causing severe damage to the belt, the tail pulley and in general to the conveyor mechanism. Even when the fugitive material is sufficiently fine or soft so as not to immediately damage the belt or the tail pulley, this type of fugitive material may build up on the pulleys and idlers thereby inhibiting the conveyor's performance and causing premature wear of the inside belt surface. Fugitive materials such as snow, ice and moisture may also accumulate on the interior side of the conveyor belt and cause slippage between the belt and the pulleys. Fugitive materials also encompass packages, bottles, tools and any other object or material which may fall upon the return run of the conveyor belt, all of which may damage the conveyor mechanism. It is therefore desirable to provide an effective means for the removal of such fugitive material from the return run of a conveyor belt.
Conveyor belt scraper mechanisms may be utilized to remove fugitive material from the inside surface of the return run of a conveyor belt. Such a scraper mechanism must be capable of self adjusting to provide effective cleaning in all states of blade wear and must also be capable of rising and falling with belt deflections caused by changes in belt tension or by belt vibration. The scraping force, the amount of force with which the scraper blade contacts the conveyor belt, required to effectively clean a belt will vary from one conveyor to the next depending upon such factors as the type of material conveyed, belt speed, and amount of belt vibration. An excessive scraping force will unnecessarily cause premature wear to the belt, while an insufficient scraping force will not effectively clean the belt. It is also desirable to have a uniform scraping force across the width of the belt to uniformly clean the belt and to avoid belt wear caused by uneven scraping forces applied between the scraper blade and the belt.
Many of the previously used scraper mechanisms are largely comprised of heavy metal parts. As the scraper blade is worn away, these metal parts may come into contact with the belt and cause considerable damage to the belt. These scraper mechanisms, or their metal parts, may also come loose from the conveyor mechanism and be carried into the tail pulley causing severe damage to the belt, tail pulley and other parts of the conveyor mechanism.
A stationary scraper mechanism is shown in U.S. Pat. Nos. 689,881 and 3,017,012. Scraper mechanisms using mechanical means for adjustment, such as hydraulic cylinders and springs, are shown in U.S. Pat. Nos. 2,909,273, 3,206,011 and 4,811,833. A rotary plow feeder is shown in U.S. Pat. No. 3,642,153. Scraper mechanisms which are pivotably connected to the conveyor mechanism are shown in U.S. Pat. Nos. 2,859,864, 3,414,116 and 3,865,232. A scraper mechanism which floats upon the conveyor belt and which is connected to the conveyor mechanism by a single chain is shown in U.S. Pat. No. 2,709,514.
Martin Engineering Company, assignee of the present application, has also manufactured and sold plow type tail protection systems as illustrated in Martin Brochure No. 3070-189 WP.